Re: GNU make troubleshooting

[Paul Smith]

I want to prefix this by saying that there's no question that make's
traceability could be improved: I'm not saying nothing needs to be
done.

On Mon, 2023-07-10 at 20:32 +0200, Bruno Haible wrote:
> 1) Print the total of the Makefile and all included Makefiles.
>    Like what "gcc -E" does with C code.

This has been requested before, but note that it's not really as useful
as people often think it will be because a lot of the internal database
of make is constructed dynamically, not directly from content in
makefiles.

I find the output of "make -p" helpful as it tells you where every rule
and variable was defined.

>    This would also answer a question on #gnu today:
>    "Is there a way to figure out where the rule is coming from? The
> main
>     issue is "target file 'clean' has both : and :: entries. Stop."
> But
>     I'm unable to figure out where the last clean: target is coming
> from."

The "last" one is the one that's referenced in the output.  Finding the
"first" one is not as easy; the error message can be improved here.  In
other similar types of messages we do show both the old and new
locations.

  $ cat Makefile
  all: ;
  all:: ;

  $ make
  Makefile:2: *** target file 'all' has both : and :: entries.  Stop.
           ^ line number if last target

Showing the "macroexpanded make sources" is difficult because make
doesn't just expand an entire line then parse it.  Makefile syntax is
context-sensitive so you can't know how or if to expand parts of a line
until you've already expanded other parts.  Of course make could keep
track of this for generating this kind of output.


> 2) Where is the Makefile source for each command that gets executed?

Have you tried using the --trace option?  This was added specifically
to provide this kind of information:

  $ cat Makefile
  all: ; @echo hi

  $ make --trace
  Makefile:1: update target 'all' due to: target does not exist
  echo hi
  hi

> 3) Single-stepping or tracing function execution.

Tracing is possible although if we just enable tracing for all variable
expansion you'll get a TON of output.  Maybe the user could ask to
trace expansion of certain things only.

I'm not interested in implementing an "interactive" mode for single-
stepping GNU Make.  Maybe someone else wants to do it but my suspicion
is that the code changes needed would be massively disruptive.

>    There is an option --eval=STRING, but I don't think it fulfils the
>    need.

No, this has nothing to do with that.